1. Field of the Invention
The present invention relates to a wavefront aberration measuring apparatus for measuring a wavefront aberration and an optical performance of a measurement target optical system, especially projection optical system provided in a projection exposure apparatus, etc. used when manufacturing a measurement target optical system, especially a semiconductor device or a liquid crystal display device, and to an aberration measuring method. The present invention relates also to a projection exposure apparatus having the same measuring apparatus, and a device manufacturing method using the same measuring method. It is to be noted that the present application is based on Japanese Patent Application No.10-153915 of which the contents are hereby incorporated by reference.
2. Related Background Art
There has hitherto been a method of using an interference optical system in the case of measuring a wavefront aberration of a measurement target optical system. According to the method based on the interference optical system, the wavefront aberration is measured by incorporating the measurement target optical system defined as a measurement target into the interference optical system, and the Twyman-Green interferometer and the Fizeau interferometer are known. For example, the Twyman-Green interferometer is constructed such that the light beam from a laser light source is divided into two fluxes of light (beam) by a half-mirror, one flux of light transmit the measurement target optical system, and the other flux of light is set as reference light beam. Then, the light beam transmitting the measurement target optical system interferes with the reference light beam, and an aberration of the measurement target optical system is measured from interference fringes thereof.
Further, what is known as a method of measuring a wavefront of the light beam from the measurement target optical system is a method called the Shack-Hartmann method using a lens array (Parity vol. 05, No. 10, 1990-10, pp. 37-39). A wavefront measurement based on this Shack-Hartmann method is that a fluctuation of the wavefront from the celestial body is measured. As shown in FIG. 9, to begin with, a wavefront (which will hereinafter be termed a [measurement target wavefront]) transmitting a measurement target optical system TL (indicating herein a telescope) is converted into parallel light beam by a collimator lens CL. Then, the parallel light beam is incident on a lens array (which will hereinafter be called a [two-dimensional lens array] where minute lenses Lxe2x80x2 are two-dimensionally arrayed. Herein, if the measurement target wavefront has a deviation from an ideal wavefront, this deviation appears to be a positional deviation of a converging position of the measurement target wavefront from a converging position of the ideal wavefront on a converging position detection unit DET. The wavefront is thereby measured based on the positional deviation of the converging position of each individual lens of the two-dimensional lens array.
There arise, however, the following problems inherent in the prior art described above. The interferometer method needs an interference optical system device used only for measuring the wavefront aberration. This interference optical system device is easy to be influenced by vibrations because of measuring the interference on the order of wavelength, and therefore requires an anti-vibration board. Therefore, this leads to a scale-up of the device, resulting in a problem of causing a decline of a using efficiency.
A main purpose of the wavefront measurement based on the Shack-Hartmann method is, as mentioned above, originally to measure the fluctuation of the wavefront from the celestial body, and therefore the Shack-Hartmann method is incapable of measuring the wavefront aberration of the lens used in the projection exposure apparatus for manufacturing a semiconductor device, etc.
In the wavefront measurement based on the Shack-Hartmann method, the two-dimensional lens array is used with a high precision, however, if there exists a scatter in terms of an accuracy of each lens of the lens array, an accuracy of detecting the converging position also declines. Hence, there might be a possibility in which the wavefront cannot be measured with the high precision.
It is a primary object of the present invention, which was devised to obviate the above problems, to provide an aberration measuring apparatus that is small in size, easy to manufacture and capable of readily measuring a wavefront aberration with a high accuracy, an aberration measuring method, a projection exposure apparatus including the same measuring apparatus, a device manufacturing method using the same measuring method, and an exposure method.
To accomplish the above object, according to the invention of aspect 1, an aberration measuring apparatus comprises a converging lens (L) for converging light beam traveling through a measurement target optical system (PL) on a predetermined surface (IP), an aperture stop (AP) for transmitting a part of the light beam, a moving unit (M) for moving the aperture stop within the flux of light (light beam), a converging position detection unit (DET) for detecting a positional deviation of a converging position (P) of a part of the light beam traveling through the aperture stop on the predetermined surface, and an arithmetic processing unit (PC) for calculating an aberration of the measurement target optical system on the basis of an output signal from the converging position detection unit.
According to the invention of aspect 2, the converging lens converges a part of the light beams, and the moving unit moves the converging lens integrally with the aperture stop in the direction intersecting the optical axis of the light beam.
According to the invention of aspect 3, an aberration measuring apparatus for measuring an aberration of a projection optical system (PL) for transferring onto, a substrate (WH), an image of a predetermined circuit pattern formed on a mask (R), comprises an aberration measuring optical system (PH) for emitting a light for measuring the aberration fall upon the projection optical system, a plurality of lens elements (Lxe2x80x2), two-dimensionally arrayed, for converging the light beam for measuring the aberration which travel through the projection optical system, a converging position detection unit (DET) for detecting each of positions of the light beam converged by the plurality of lens elements, and a measuring device (PC) for measuring the aberration of the projection optical system on the basis of the converged light beam positions detected by the converging position detection unit. Herein, the aberration measuring optical system may embrace pinholes of a reticle or a stage, or a transmission member for transmitting the light beam in diffusion, which will be mentioned later on.
According to the invention of aspect 4, the aberration measuring optical system may include a mask (R) for measuring the aberration, disposed substantially in the same position as the mask formed with the predetermined circuit pattern is disposed and having a pinhole pattern, and an illumination optical system (1 to 10) for illuminating the mask for measuring the aberration with the light beam.
According to the invention of aspect 5, the illumination optical system may be an illumination optical system (1 to 10) for illuminating the predetermined circuit pattern with the light beam.
According to the invention of aspect 6, an aberration measuring method comprises a step for converging light beams traveling through a measurement target optical system (PL) on a predetermined surface by the use of a converging lens (L), a step for making an aperture stop transmit a part of the light beam;
a moving step for moving the aperture stop (AP) with the flux of light a converging position detecting step for detecting a positional deviation of each of a converging position (P) of a part of the light beam traveling through the aperture stop on the predetermined surface by the use of a converging position detection unit (DET), and an arithmetic processing step for calculating an aberration of the measurement target optical system on the basis of an output signal obtained in the converging position detecting step.
According to the invention of aspect 7, a part of the light beam is converged in the converging step, and the converging lens is moved integrally with the aperture stop in the direction intersecting the optical axis of the light beam in the moving step.
According to the invention of aspect 8, an aberration measuring method of measuring an aberration of a projection optical system (PL) for forming, on a substrate (WH), an image of a predetermined circuit pattern formed on a mask (R), comprises a step for converging the light beams for measuring the aberration that have passed through the projection optical system by the use of a plurality of lens elements (Lxe2x80x2), two-dimensionally arrayed a step for detecting each of positions of the light beams converged by the plurality of lens elements, and a step for measuring the aberration of the projection optical system on the basis of the detected light beam positions.
According to the invention of aspect 9, the light beam for measuring the aberration is light beam from a pinhole pattern (PH) on a mask, for measuring the aberration, disposed substantially in the same position as the mask is disposed.
According to the invention of aspect 10, a projection exposure apparatus comprises an illumination optical system (1 to 10) for illuminating a predetermined circuit pattern with the light beam, a projection optical system (PL) for forming the circuit pattern illuminated with the light beam on a substrate (WH), and an aberration measuring apparatus, of aspect 1, for measuring an aberration of the projection optical system.
According to the invention of aspect 11, a projection exposure apparatus comprises an illumination optical system (1 to 10) for illuminating a mask (R) having a predetermined circuit pattern with the light beam, a stage (11) for supporting the mask, a projection optical system (PL) for forming on the substrate an image of the circuit pattern illuminated with the light beam, and an aberration measuring apparatus, of aspect 1, for measuring an aberration of the projection optical system. The stage or the mask has a generation member (PH) for generating light beam for measuring the aberration of the projection optical system.
According to the invention of aspect 12, the generation member is a pinhole pattern (PH) for converting the light beam from the illumination optical system into spherical waves.
According to the invention of aspect 13, the generation member may be a transmission member for transmitting in diffusion the light beam from the illumination optical system.
According to the invention of aspect 14, a projection exposure apparatus having a projection optical system (PL) for transferring onto a substrate (WH) an image of a circuit pattern formed in a mask (R), comprises an aberration measuring optical system (PH) for emitting a light beam for measuring the aberration upon the projection optical system, a lens array (Lxe2x80x2) for converging the light beams for measuring the aberration which travel through the projection optical system, and a converging position detection unit (DET) for detecting each of positions of the light beams converged by the lens array.
According to the invention of aspect 15, the aberration measuring optical system may include a mask (R) for measuring the aberration, disposed substantially in the same position as the mask formed with the predetermined circuit pattern is disposed and having a pinhole pattern (PH), and an illumination optical system (1 to 10) for illuminating the mask for measuring the aberration with the light.
According to the invention of aspect 16, the projection exposure apparatus may further comprise a control unit (LC) for controlling a position of at least one of optical members constituting the projection optical system on the basis of a detected result given from the converging position detection unit.
According to the invention of aspect 17, the projection exposure apparatus may further comprise a substrate stage (13) for holding the substrate. At least the lens array or the converging position detection unit may be detachably provided on the substrate stage.
According to the invention of aspect 18, a device manufacturing method including a step for transferring an image of a predetermined circuit pattern onto a substrate (WH) by the use of a projection optical system (PL), comprises a step for measuring an aberration of the projection optical system by the use of the aberration measuring method of aspect 6.
According to the invention of aspect 19, a device manufacturing method including a step for transferring an image of a predetermined circuit pattern onto a substrate by the use of a projection optical system (PL), comprises a step for measuring an aberration of the projection optical system by the use of the aberration measuring method of aspect 8.
According to the invention of aspect 20, an exposure method comprises a step for exposing a substrate to the light beam of a predetermined circuit pattern in a way of projecting the circuit pattern on the substrate by the use of the projection exposure apparatus of aspect 11.
According to the invention of aspect 21, an exposure method for transferring onto a substrate (WH) an image of a predetermined circuit pattern by the use of a projection optical system (PL), comprises a step for making light beam for measuring an aberration incident upon the projection optical system before transferring the circuit pattern onto the substrate, a step for converging the light beam for measuring the aberration that have passed through the projection optical system by the use of a plurality of lens elements (Lxe2x80x2) two-dimensionally arrayed, a step for detecting each of positions of the light beams converged by the plurality of lens elements, a step of measuring the aberration of the projection optical system on the basis of the detected positions of the light beams, and a step for correcting the aberration of the projection optical system on the basis of the measured aberration.
According to the invention of aspect 22, the aberration may be a wavefront aberration of the projection optical system.
According to the invention of aspect 23, an exposure apparatus having a projection optical system (PL) for transferring onto a substrate (WH) an image of a pattern formed on a mask (R), said apparatus comprises: and a holding mechanism for detachably holding the aberration measuring apparatus of aspect.
According to the invention of aspect 24, the holding mechanism may include a first holding member (11) for holding an aberration measuring optical system, and a second holding member (12, 13) for holding a measuring unit (UTxe2x80x2) having a plurality of lens elements, a converging position detection unit and a measuring device.
According to the invention of aspect 25, the first holding member may be a mask stage (11) for holding the mask, and the second holding member is a substrate stage (13) for holding the substrate.
According to the invention of aspect 26, the aberration measuring optical system may be a mask (R) for measurement, formed with a pinhole pattern (PH) for measuring the aberration.
According to the invention of aspect 27, an aberration measuring apparatus for measuring an aberration of a projection optical system (PL) for transferring onto a substrate (WH) an image of a pattern formed on a mask (R), comprises a measuring unit (UTxe2x80x2) detachably provided on an exposure apparatus including a mask stage (11) for holding the mask, the projection optical system, and a substrate stage (13) for holding the substrate. The measuring unit may Include a plurality of lens elements (Lxe2x80x2), two-dimensionally arrayed, for converging light beam for measuring an aberration that have passed through the projection optical system, a converging position detection unit (DET) for detecting each of positions of the light beams converged by the plurality of lens elements, and a measuring device (PC) for measuring the aberration of the projection optical system on the basis of the light beam positions detected by the converging position detection unit.
According to the invention of aspect 28, the aberration measuring apparatus may further comprise an aberration measuring optical system (PH) through which the light beam for measuring the aberration fall on the projection optical system. The measuring unit may be detachably held on the substrate stage, and the aberration measuring optical system is provided on the mask stage.
According to the invention of aspect 29, an aberration measuring method for measuring an aberration of a projection optical system (PL) incorporated into an exposure apparatus for transferring onto a substrate (WH) an image of a pattern formed on a mask (R), comprises a step for disposing an aberration measuring optical system (PH), for emitting a light beam for measuring the aberration fall upon the projection optical system, substantially in the same position as the mask is disposed, and a step for attaching, to a substrate stage (13) for holding the substrate, a measuring unit (UTxe2x80x2) including a plurality of lens elements (Lxe2x80x2) for converging light beams for measuring an aberration that have passed through the projection optical system, a converging position detection unit (DET) for detecting each of positions of the light beams converged by the lens array, and a measuring device (PC) for measuring the aberration of the projection optical system on the basis of the light beam positions detected by the converging position detection unit.
According to the invention of aspect 30, an aberration measuring method may further comprise a step for removing the aberration measuring optical system after the light beam for measuring the aberration have fallen upon the projection optical system, and a step for removing the measuring unit from the substrate stage after measuring the aberration of the projection optical system.
According to the invention of aspect 31, an exposure method for transferring onto a substrate (WH) an image of a predetermined circuit pattern by the use of a projection optical system (PL), comprises a step of measuring an aberration of the projection optical system by the use of the aberration measuring method of aspect 29 before transferring the circuit pattern onto the substrate.
According to the invention of aspect 32, a device manufacturing method including a step of transferring onto a substrate (WH) an image of a predetermined circuit pattern by the use of a projection optical system (PL), comprises a step of measuring an aberration of the projection optical system by the use of the aberration measuring method of aspect 29 before transferring the circuit pattern onto the substrate.